Mischmetal-magnesium pellets and process for manufacturing the same



Unitid States Patent MISCHIVIETAL-MAGNESIUM PELLETS AND PROC- ESS FOR MANUFACTURING THE SAME Isidor S. Hirschhorn, West Orange, NJ., assignor to Ronson Metals Corporation, Newark, N.J., a corporation of New Jersey No Drawing. Filed Jan. 16, 1957, Ser. No. 634,404 Claims. (Cl. 29-528) The present invention relates to the manufacture of pellets made from an alloy containing mischmetal and magnesium.

It is one of the primary objects of this invention to provide means facilitating the production of mischmetalmagnesium alloy in extruded rod or bar formation for obtaining therefrom pellets for use in connection with production' of nodular iron, high-precisi0n structural metal and light metal parts, such as aircraft engine cylinder blocks, manifolds, and like components, Whose composition is to be closely and accurately controlled and maintained.

Another object of the present invention is to provide means rendering the possibility of producing complementary alloy additions principally composed of magnesium and mischmetal, which are to be incorporated in a predetermined rare earth alloy melt to make up the finally required composition for the manufacture of high precision structural part or parts.

Still another object of the present invention is to provide means leading to a higher yield of rare earth metals in the finished composition, as the burning-01f of said additions of mischmetal-magnesium in the melt is minimized and saving of said addition alloy material may be attained, as the dissolution of said addition alloy material in pellet form occurs quite rapidly and before these additions are ableto reach the bottom of the crucible containing the melt which may be composed of magnesium-zirconium-rare earth metal (mischmetal).

Yet a further object of the invention is to provide means alfording an eflicacious production of pellet-shaped alloy additions of the aforesaid type ofiering great resistance to corrosion, even during prolonged storage thereof. Yet another object of the invention is to provide pellets from extruded shapes which are highly economical to produce and may be readily adjusted to the required proportionate quantity as these shapes may he changed in their dimensions (e.g. length or thickness) without encountering. any difiiculties, as compared with heretoforeusual practice, according to which alloy additions were presented in bulky and-difiiculty controllable cast form.

A still furtherpbject of the present invention is to provide rneaiis affording economic and dosed packagingof pellet-shaped alloy additions of predetermined weight in cans or like containers without dimension of air thereto, if desired.

Other objects and advantages of this invention will become apparent from the description and claims which follow.

The invention may be best understood under consideration of the following example, which is given only for comprehending and appreciating the invention and not in a limitative sense.

In accordance with the present invention a billet having a diameter of about 30 mm. and composed of mischmetal-magnesium alloy, in which magnesium is contained from about 2% to by weight, is subjected to extrusion in an extrusion press whereby the extrusion or work- "ice ing pressure may vary between approximately 11,000 to 15,000 kg./cm. depending upon the quantity of magnesium employed. It has been found that magnesium in the amount of approximately 8.25% requires an extrusion or working pressure of about 11,000 kg./cm. whereas a content of magnesium of 12.5% by weight or more does not permit such mischmetal-magnesium alloy to be subjected to extrusion.

In order to produce said billet mischmetal and magnesium are melted in the desired proportionate quantities and by pouring said ingredients at about 1,000 C. the billet is obtained.

The billet will then be heated to 500 C. and subjected to extrusion at a pressure of approximately 15,000 kg./ :m. to bring about a rod having a diameter of about .156 of one inch, from which are cut ofi pelletor cylinder-shaped bodies having a length (thickness) of about 4" so that the pellet bodies may be employed as accurate additions of any suitable alloy or composition. About 880 pellets will amount to 1 lb. and may be packaged in suitable cans containing from 5 to 100 lbs., respectively.

These pellets may, for example, be used as additions to the melt of a magnesium-zirconium-mischmetal alloy containing primarily magnesium, with zirconium amounting to 0.2l.0% by weight and mischmetal amounting to about 2.5% to 5.0% by weight of the alloy.

The melt temperature in the crucible containing the aforesaid magnesium base metal with the additions of zirconium and mischrnetal ranges between 1450 and 1500 F.

Another example for using pellets of extruded mate} rials either in the form of pure mischmetal or mischmetal together with magnesiumand iron, such as, for example, by weight of mischmetal, 23 by weight of iron and 2% by Weight of magnesium is to employ such material in the production of nodular iron, the diameter of each pellet being approximately .156 of one inch whereas the length of each pellet may be about A of one inch. The shape of the pellets is generally cylindrical, but other shapes, such as bar-shaped or hexagonal-shaped rod ma terial, are also suitable as long as they contain respective proportionate amounts of the required ingredients and as long as such shapes were obtained through the extrusion process, as above stated and make up the required addi tions for the respective melt, such as, for instance, 0.15% to 0.50% mischmetal.

The advantages hereinabove enumerated are of great importance as it is now possible to predetermine and to precisely adjust the proportionate amount of constituents or ingredientsto beadded for obtaining faultless structural parts for use in high precision engines and like parts. H g

To elucidate how the invention may be carried out in practice the following is to he noted:

(A) pounds of molten cast iron are tapped from a cupola into a ladle at 2800 F. While in the ladle .25 pound-of an additive obtained from an extruded alloy rod (in the form of about 200 pellets) consisting of about 75% of cerium (mischmetal), about 23% of iron and about 2% of magnesium are wrapped in a perforated iron screen and added to the ladle for mixture with the contents thereof. When the temperature is reduced to about 2700 F., the metal is poured after skimming the melt in accordance with standard practice. The result of this additive is to substantially pinpoint the final iron composition and to determine its strength and ductility.

(B) To obtain 60 lbs. melt of a final alloy containing approximately 2.5% to 4.4% of cerium (mischmetal), up to 0.3% of zinc and about 0.2% of zirconium, with magnesium forming thebalance about 1.8 lbs. of misch metal or rare earth metals are required. Accordingly,

2 lbs. of an extruded specific alloy consisting of about 90% mischmetal and about magnesium or approximately 1760 pellets obtained from said extruded alloy are used, which are added to a magnesium melt prepared in a, gas fire-d crucible in accordance with standard practice, the temperature being about 1400 F. After complete melt -down-of magnesium (about 57.9 lbs.) the temperature is raised to 1450-1500 -F. and as an additive 1760 pellets of the aforesaid specific alloy with a predetermined quantity of zinc (0.18 lb.) are placed into a ladle and then added to the melt.

Thereafter a predetermined quantity of a magnesiumzirconium alloy (0.12 lb.) is added. After maintaining this melt at a temperature of 1450l500 F. for about minutes, the temperature is adjusted for pouring and the metal poured in accordance with standard practice to bring about-precision castings or parts, as desired.

If only a 10 lbs. melt were required, 0.33 lb. of the aforesaid specific alloy*(amounting to approximately 300 pellets) can be precisely added.

Accurate additions of small quantities of the aforesaid specific extruded alloy may accordingly be made regardless of the size of the melt. This is not possible when mischmetal alloys in the commonly available cast ingot form are used.

It can thus be seen that in accordance with the invention there has been provided a new process and additive for carrying the same into efiect.

The additive may be used in connection with any alloy melt and comprises a plurality of alloy pieces of uniform size and in pellet form and cut from extruded alloy shapes, each piece containing constituents in respective proportionate amounts complementary to the final alloy composition.

Although specific embodiments of the invention have been described, it should be noted that the invention may be realized in modified form and adaptations of the arrangements herein disclosed may be made, as may readily occur to persons skilled in the art without constituting a departure from the spirit and scope of the invention as defined in the objects and in the appended claims.

It is apparent from the above description that in accordance with the invention a final alloy composition having precisely determined constituents may be obtained by providing a preliminary melt having a precisely determined relation to the final composition, and selecting a number of alloy pellets of uniform thickness and composition derived from extruded metal rod and providing in their aggregate precisely measured constituents complemental to the constituents of the preliminary melt for producing the final alloy composition when added to the melt. This selected number of these pellets is then added to the melt so as to provide with the melt the final alloy composition.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A process for obtaining a final alloy composition having precisely determined constituents; comprising the steps of preparing a preliminary melt of a magnesium base alloy consisting of mischmetal of about 2.5% to 5% by weight and zirconium of about 0.2% to 1% by weight, adding to said metal a predetermined number of pellets of uniform thickness and composition and cut from lengthy extruded rod of mischmetal-magnesium alloy with a magnesium content ranging from 2% to 10% by weight and mischmetal forming the remainder of said mischmetal-magnesium alloy, the number of alloy pellets being complementary to the final magnesium base alloy composition, and conditioning said melt to absorb said pellets thereby to obtain said final alloy.

2. A process according to claim 1, said extruded rod being obtained by first pouring magnesium and mischmetal at about 1000" C. into the form of a billet, heating the billet about 500 C., subjecting the heated billet to extrusion at a pressure of approximately 15,000 kg./cml to extrude to alloy rod of a diameter of about 0.156 inch, and then cutting fromsaid rod said pellets each of a thickness of about 0.25 inch.

3. An additive for use in connection with an alloy melt consisting of a magnesium base'alloy including mischmetal of about 2.5% to 5% by weight and zirconium of about 0.2% to 1% by weight, for preparing final alloy composition; comprising'a plurality of alloy pieces of uniformsize and in pellet form and cut from extruded alloy shape, each pellet containing constituents in respective proportionate amounts complementary to said final alloy composition, said extruded alloy shape being a mischmetal-magnesium alloy having a magnesium content ranging from 2% to 10% by weight, mischmetal forming the remainder of said alloy.

4. An additive for use in connection with an alloy melt containing mischmetal; comprising pellets obtained from the extrusion of an alloy consisting of mischmetal in the amount of about by weight and magnesium of about 10% by weight.

5. An additive for use in connection with an alloy melt containing mischmetal; comprising pellets of uniform size cut from extruded alloy consisting of magnesium ranging from 2 to 12% by weight, the remainder being mischmetal, whereby said magnesium forms a stabilizing agent for said mischmetal alloy to prevent oorrosion and disintegration of said mischmetal.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Metals Handbook, 1948 Edition, p. 9, American Society for Metals. 

